Murder mystery writer Agatha Christie wanted to “exorcise herself” of Poirot, one of her most famous and enduring characters, her grandson has revealed.

Mathew Prichard said that the novelist came to think of the Belgian detective as her “bread and butter” but would complain about having to churn out “yet another Poirot”.

Speaking before The Halloween Party on ITV1, the 63rd TV adaptation of one of Christie’s Poirot detective stories, he told the Radio Times: “She was never short of ideas for books but some of these ideas were inappropriate for Poirot, so she was very keen to exorcise herself of him by writing different stories with new characters.

“But her agents and publishers, who were in charge of the pounds and pence, were very keen on Poirot - he was her most popular character.”

Christie, deemed the world’s best-selling author, signed over the rights of her favourite works to her daughter and grandson before her death at the age of 85 in 1976.

Mr Prichard, who has read all of his grandmother’s books, watched every drama and listened to every radio adaptation, said: “She was a very generous person and when I was nine she signed The Mousetrap over to me.

“I was too young to appreciate it at the time, but it now has a business history as long as my arm.”

But he said it was not until he reached the age of 10, when he picked up a book from her shelf in her cliff-top Devon home and started reading it, that he realised his grandmother wrote crime novels.

“It wasn’t one I would choose for a 10-year-old. There are 10 murders in And Then There Were None and some are pretty gruesome,” he said.